Cardiovascular System Flashcards
What does the cardiovascular system consist of?
The heart and blood vessels.
What are the two aspects of the cardiovascular system?
Conduction System and mechanical pump
both must function for normal heartbeat to occur
What makes up the conduction system?
SA node, AV node, bundle of HIS, right and left bundle branches and Purkinje fibres
Where does the conduction system initiate?
In the SA Node (100bpm)
How many BPM does the AV node depolarise to?
40-60bpm
What is the equation for Cardiac output?
Heart Rate X Stroke Volume
What is the equation for blood pressure?
HR X SV= CO and SVR
What does SVR stand for?
Systemic Vascular Resistance
What do we need to maintain blood pressure?
An effective pump and venous return (preload) and pressure in the system (Afterload)
What are the two vital aspects of Cardiac Function?
Electrical activity and mechanical activity- if either fail the heart fails
What does the cardiac system contain?
It’s own autorhymicity
What is the SA Node?
It is normally the pacemaker of the heart 60-100bpm
What can act as a secondary pacemaker if SA Node fails?
AV Node- 40-60bpm
what can the cardiac conduction system be affected by?
Sympathetic and Parasympathetic nervous system
In the hearts mechanical pump- why is the left ventricle wall thicker than the right ?
due to the need to generate higher pressures in systemic arteries
What does myocardial contraction rely on?
Actin Myosin Sliding Filaments
What is required for a strong contraction to occur?
Calcium as it binds to the actin
What energy does contraction require?
high levels of energy in the form ATP- it also requires a huge amount of O2
What is the hearts demand for blood supply?
5% total cardiac output
what happens if there is a disruption to the supply of O2?
It can lead to arrthymias or damage to the muscle
how much roughly of total body mass does the heart make up?
about 0.3%
where is venous blood collected?
The Coronary Veins
where does the venous blood drain directly to?
Drains directly into the right atria via the coronary sinus
what are the two main phases of the Cardiac Cycle?
Diastole (relaxation) and Systole (contraction)
How long on average does a full cycle take?
0.8 seconds
what is the longest period of the Cardiac Cycle?
Diastole as this allows time for the atria and ventricles to fill
what is the cardiac cycle driven by?
venous return from the superior and inferior vena cava
what happens as the atria fills?
The volume exerts a pressure onto the AV valves
What happens when the ventricles relax?
pressure gradient increases
What happens when an MI affects the papillary muscles or valve infections?
It can cause malfunction of the valve (infective endocarditis)
where do the veins carry blood to?
Back to the heart
where do arteries carry blood from?
The Heart
what has a vital role in maintaining BP?
Vascular System
what affects Systemic Vascular resistance (SVR)?
dilation and constriction
What is the filling of any heart chamber influenced by?
Venous return
What are the two types of BP Control?
Neutral control and hormonal control
Where is the nervous control managed in the brain?
It is managed by the cardiovascular centre in the medulla and pons of the brainstem
Where are the cells that detect a reduction in renal blood flow and release renin?
Juxtaglomerular Apparatus
Where does Renin convert Angiotensionogen to angiotensin I?
The Liver
where is angiotensin I converted to angiotensin II?
The lungs
Where is the antidiurectic hormone found?
posterior pituitary gland
What does Angiotensin II stimulate?
It stimulates vasoconstriction of smooth muscle in the arterial circulation- increasing SVR
What does ANP stand for?
Atrial Natriuretic Peptide
What is ANP?
it is a hormone released in the heart when blood volume becomes great enough to stretch the atrial wall beyond normal
